Mining machine



Oct. 9 1923.

' G. R BENNETT MINING MACHINE Filed April 21, 1919 6 Sheets-Sheet 1 l l I I I l ll llllllllll I?! llr lllllllll ll u I lllll I ||||II|.|.|+|| lbl l l I I I l I I I I Q. mm

INVENTOR Oct. 9 1923.

G. R. BENNETT MINING MACHINE Filed April 21 1919 6 Sheets-Sheet 2 WITNESSES N G. R. BENNETT MINING MACHINE Filed April 21, 1919 6 Sheets-Sheet 4 INVENTOR Oct. 9 1923.

- G. R. BENNETT MINING MACHINE Filed April 21, 1919 6 Sheets-Sheet 5 W S F WITNESSES Oct. 9 1923.

G. R. BENNETT MINING MACHINE 1919 6 Sheets-Sheet 6 Filed April 21 INVENTOR ill Patented Oct. 9, 1923.

uurrso srnres PATENT OFFICE.

GEORGE It. BENNETT, OF PITTSBURGH, PE"NNSYLVANIA.

, MINING MACHINE. I

Application filed April 21, 191.9. Serial No. 291,482.

unprovenients the following is a speciiication.

The invention described herein relates to certain improvements in mining and tunnelling machines, and has for its object a construction and combination of elements embodying a plurality of drilling devices, a plurality of hammers, subject to fluid pressure operating continuously to shift the hammers in a direction to cause the drilling devices to penetrate the rock, etc., and intermittently operative means for moving the hammers against the continuously operating pressure. It is a further object of the invention to provide for the rotation of the drilling devices at intervals inter-1 mediate the forward or operative rnove ments of the hammers and to provide for indicatingto the operator the inoperativeness of any of the drilling devices, and to automatically stop the machine in case the operator fails to notice the indication. The invention is hereinafter more fully described and claimed.

In the accompanying drawings forming a part of this specification, Fig. 1 is a side elevation and Fig. 2 a top plan view of the main or carrying frame of the machine; Figs. 8 and 4t are horizontal and vertical sections respectively of the parts directly operative for driving and rotating the drills; Figs. 5 and 6 arehorizontal and vertical sections showing the mechanism for rotating the drill spindles and the connections from the pressure cylinder to operate the drill rotating mechanism; Figs. 7, 8, 9 and 10 are sectional details on an enlarged scale, showing the mechanism for moving the hammers rearwardly against the pressure in the hammer cylinder; Fig. 11 is a sectional detail view of one of the drill spindles and its supporting and operative parts; Fig. 12 is a sectional elevation of the spindle box or head, the

plane of section being indicated by the line XlL-XII, Fig. 3; Fig. 13 is a sectional view on a plane indicated by the line XIII'**-J.III, Fig. 11; Fig. 14 is a 'ing the shaft is shifted.

section on a plane indicated by the line XTVXIV, Fig. 3; Fig. 15 is a front elevation of a head for holding broken rock in place during the drilling operation.

In the practice of the invention, power is applied through asuitable train of gearing to the main shaft 1 of the machine by any suitable form or construction of. motor, which ispreferably carried on the rearward extension of the platform 2. This platform is so mounted in themain frame of the machine as to be capable of vertical movement therein, for the purpose of changing the field or area of operation, as hereinafter described. As it is preferred that the platform should have a pivotal movement, it

is supportedadjacent to its rear end by a transverse beam 3, having rollers 4, loosely mounted on journals at its ends, said rollers being supported by short rails 5 secured at their ends to vertical posts of the main frame.

to intermesh-with similar gears 12 on'the transversev shaft 13. This shaft is rotated to turn the nuts by a countershaft 16,

mounted in suitable hearings on the plat form and engaging the shaft '13 through beveled pinions 14: and 15.

The nuts 7 i The vertical movement of the front {end of the platform can be effected by any In the construction shown, the counter shaft, 16 is driven by the main shaft through .a sprocket chain 17, passing around toothed wheels on the main and countershafts the sprocket wheel on the shaft 1 being so spliued thereto as shown in Fig. 1, as to permit the shaft to slide through the sprocket wheel when the platformf2carry- The wheel on the countershaft being loose is adapted to be connected thereto by a clutch mechanism 18. The shifting of the movable member of the clutch is effected by a lever 19 when the vertical, movement, either up or down, of

the platform is desired. The front end of the platform rests upon rolls, 20, loosely mounted upon thecross head 9. The longitudinal movement of the platform on the supports just described, is effected by any suitable means, preferably that clearly shown in Figs. 1 and 2. A shaft 21 is mounted in suitable hearings on the platform 2 and is adapted to be rotated by the main shaft 1 through suitable intermediate gearing; This shaft is provided with a worm 22 intermeshing with worm-wheel 23 on the transverse shaft 24L which is provided with a pinion 25 adapted to intermesh with a toothed bar 26, pivotally connected at its front end, to the cross head 9, so that on the rotation of the pinion 25, the pl'atforn'i will be caused to move forward, the pinion intermeshing with the rack bar, rolling over same. The rack bar i held normally up in engagement with its interineshing pinion by any suitable means, so constructed as to be "capable of being quickly shifted to permit of the dropping of the raclobar in case of emergency.

In the construction shown, the rack-bar is supported so as 'to' be engaged by' the pinioi'i 25 by a cam 27 on the shaft 2.8,which is provided with an operating lever 29. As it would be frequently desirable to stop operation of the entire machine simultaneously with the disengagement of the rackbar from the pinion 25, the lever 29 con-- nected by a. detachablelink 30 to the lever 31, employed for shifting the movable member 32 of the clutch mechanism. connecting the train of gearing interposed between the motor shaft 33 and the main shaft 1 of the machine.

The main frame is so mounted on a truck 34 as to be capable of beingadjusted transversely of the truck. The truck is provided with wheels runnin -on rails 35, one pair of wheels being driven by any suitable means, preferably that shown and described herein, consisting of a chain 36 passing around a sprocket wheel slidablysecuii'ed on the axle of the rear pair of wheels, and a similar wheel 37. loosely mounted. on a shaft 38 which is support-ed in suitable hearings on the main frame. The sprocket wheel 37 is adapted to be operatively connected by a .clutch mechanism 39 to the shaft 33;. which is provided with a worm wheel T0, intermeshing with a worm 41, mounted on the shaft 21 when it is desired to move the truck along. its supporting rails, the clutch 39 thereby locking thesprocket wheel 37 to the shaft 38. The main frame is preferably supported on the truck 34 by means of wheels 42, movable along rails-l3 arranged trans versely of the truck. The wheels one side of the frame are secured on a longitu- {dinal shaft 4 1, having a Worm wheel. keyed thereon, and intermeshinp," with a, worm 41-6 loosely mounted onthe shaft 38. The worm i adapted to be locked to the shaft 38 when it is desired to shift the main frame on the truck, by a clutch mechanism l? shown in Fig. 2.

As shown in Figs. 3 and l, a chamber or cylinder 48 is carried on the front end of the movable platform 2, the connection between the cylinder and the platform being such as to permit of the cylinde and parts carried thereby being moved horizontally at an angle to the platform. This cylimlcr which is connected to a suitable supply of fluid under pressure, contains the hamn'iors employed for propelling the drills, the

mechanism for pulling the hammers back against such pressure, and the mechanism for transmitting power to the multiple drill head, which contains the mechanism for rotating the drill spindles. The dimensions of the cylinder will. depend upon the number of and arrangement of the drills employed.

The power shaft 1 has secured to its end a beveled pinion inter-meshing with acor-- responding pinion 50, on the shaft 5 This shaft 51 extends through a stufling be); 52 into a rearward extension 53 of the cylinder, and on the portion of the shaft enclosed in this extension is secured a sprocket wheel operatively connected by a chain 55 to a sprocket wheel on the shaft 56, mounted in suitable bearings within the cylinder. The.

shaft 56 is provided with a plurality of cranks and on the pins of these cranks are mounted blocks adapted to reciprocate in yokes which are movably mounted on guide bars. The outer yokes 60 are connected to the pulling heads 61 which are mounted on guide rods 62. The movement imparted to the blocks 57 in the respective yokes by the crank pins, will impart a horizontal re ciprocation to the members connected thereto. The front portionsof the hammers 63, which are thrust foru ird to strike the drill spindles by the pressure constantly maintained in the cylinder or box l8, project through stufing boxes ()4 on the front end of the cylinder and have their rear portions within the cylinder, movably mounted in sleeves 65 as shown in Figs. 7 to l0. The return or rearward movements of the hammers are effected by suitable mechanism carriedby the pulling heads 61. As the position of each of the hammers at the end of each blow is dependent upon the depth to which the drill has been driven, the pulling mechanisms are adapted to engage the hammers at any point intermediate the extreme rearward and forward limits of their movements. v

The hammers are arranged within the cylinder in series of rows, preferably vertical, as shown in F igs. 4c and 12, and a pulling head 61 is provided with each row or series of hammers, and the crank pins, operating the yokes connected to the pulling into oppositely inclined grooves a.

heads are so arranged around the shaft 56 that the pulling heads will be operated in sequence and not simultaneously in the same direction.

Tn the construction shown herein, the hammers 63 are provided with lines of teeth 66 on the portions within the cylinder 48. and for each hamn'ier, a pair of fingers 67 are so pivotally connerr ted to the pulling heads that: their respective lines of movement will be on diametrically opposite sides of the hammers. The fingers are provided with teeth along the inner edges, adapted to engage the teeth on the hammers, the guide sleeves being' slotted to permit of such engagement of the teeth on the fingers with those on the hammers. The front ends of the fingers are provided with laterally projecting arms 67, having loosely mounted thereon rollers 68, adapted to project The outer walls 69 of these grooves are pivotally mounted and are normally held parallel with the inner or stationary walls by springs 70, as shown in Figs. 7 to 10. The fixed walls of the guide grooves are so arranged that when the rollers 68 rest on such walls adjacent to its front end, the teeth on the fingers will engage those on the hammers.

The guide groves are so inclined that the movement of the rollers from right to left in Figs. 8 and 9 will pull the fingers out of engagement with the hammers, the time of release being; dependent upon the portion of the fingers intermediate of its ends in engagement with the hammers. grooves are made of a length substantially equal to the maximum stroke of the hammers. The outer walls 69 of the grooves being yieldingly held as above stated, will move outwardly as the fingers move forward, permitting the teeth on the fingers to slide over those on the hammers, but will cause the fingers (to engage the hammers when the fingers begin their backward stroke.

By reference to 8 and 9 it will be seen that the pivotal points of the fingers and the outer ends of the fixed walls of the guide grooves are arranged in the Suhstantially same planes which are parallel with the axes of the hammers, and in such relation to the hanuners that when the ilHQQI'S are at the end of their movement to the right. the teeth on the fingers will engage those on the hammers regardless of the longitudinal. positions of the latter. By reason of the location of the pivotal points of the fingers and the relative arrangement of the guide grooves a, it follows that if the hammers are in positions to be engae'ed by the outer ends of the fingers or points adjacent thereto. by a comparatively short movement of the fingers tothe left, they will be disengaged from the hammers and The and sleeves angu ar shown in Fig. 13 that the spindles will be the latter permitted to be shifted. by the pressure within the cylinder 48. On the other hand. i f the hammers are engaged by teeth nearer the pivotal points of the fingers, a longer movement of the fingers to the left will be required to release the hammers from the fingers.

At the beginning of a drilling operation, the hammers Wlll be at the limit of their drills hearing.

beginning of the drilling operation,before being released, as hereinhefore described, to permit of the forward. thrust of the ham mers against the drill spindles by the pressure in the cylinder. As the platform 2 and the parts carried thereby are moved forward andthe drills are forced forward into the rock at each stroke. the fingers will engage the han'uners at points nearer the rear ends of their toothed portions, and each succeeding blow on the drill spindles will be more efiective. While all the hainm of each row or series will be drawn back simultaneously, the extent of such hack movement of the several hammers n'ia -c be different, and will be dependent upon the rolati epenetration of the drills into the rock. The spindles 71, in Figs. 3, 4. l1. and 12, through which the blows of the hammers are transmitted to the drills, are

mounted in suitable hearings in the front and rear sides of the box 72, which is con neeted to the cylinder 48 by arms 72-, and in this box is arranged suitable mechanism for rotating the spindles and the drills carried thereby, as shown in Figs;

3, 4i, 5, 6. 11 and 12. A. suitable mechanism for rotating the spindles. con asts of ratchet Iwheels 74. mounted hereinafter ilescrilzml on spindles, and slides movahly mounted on a guidehar 76 suitably supported in the box. The slides are provided with spring actuated pawls 77, adapter to engage the ratchet wheels when the slides are moved. in one direction and to slide over the ratchet wheels on the reverse movement of the slides. Reverse rotation of the ratchet wheels and spindles prevented by palwls 78. Tn order to permit the spindles moving longitudinally through the rotating devices. the ratchet wheels 7-4; are loosely mounted. as hereafter described. on sleeves 79. through which the spindles pass. the spindles and sleeves being: so lOC ed one to the other. preferably hy making the external and internalcontoi'irs of the spindles in cross-section. as

rotated by the sleeves. but will be free to slide longitudinally through the latter as shown in Fig. 11.

The spindles and drills should be arranged in rows vertically and horizontally as when employing the mechanism shown herein, for rotating the spindles, it is preferred to arrange the slides vertically, so that the weight of the slides will hold the outer ends of their operating levers against the cams 81. secured to the shaft- 82. This shaft is provided at one end with a bevelled pinion 84 intermeshing with a corresponding pinion on the shaft 85, mounted in hearings in brackets 85 secured to the cylinder 48 and box 72. This shaft 85 is driven from the shaft 56, which projects through a stufiing box on theside of the cylinder d8 and is opera-tively connected to the shaft 85 through bevelled pinions 8a- In order to prevent injury to the mechanism, by reason of a drill. becoming fired in the hole it is forming, provision is made for detachably connecting the mechanism for rotating the drills to the drill spindles. in the construction shown, the ratchet wheels 74 are connected by short sleeves 86 to heads 87 in which are formed pockets S8 for the re ception of steel balls" 89, adapted to project a short distance into circular seats in the sleeves 79. surrounding the spindles, as shown in Fig. 11. The halls are yieldingly held in engagement with the seats by springs 90, the tension of the springs being sufficient to ensure the rotation of the spindles under normal working conditions, but to yield and allow the balls to be forced out of the seats in case of abnormal resistance to the rotation of the drills and spindles. Provision should be made also for indicating to the operator the failure of any drill to move progressively inward at approximately the same rate as the other drills. In order to give the indications of the failure of any oft-he drills to rotate. contact fingers 91 are so connected to the springs employed for holding the balls in their seats, as for example making the fingers integral with the springs that when the balls are unseated, the fingers will be caused to contact with rings 92, surrounding the heads 87 and se cured to a block 93" of insulating material. A suitable electric generator has one pole connected to each of the rings 92, and its other'pole to the machine or directly to the contact fingers 9]., see Fig. 13, and in the circuits thus formed, are included indicators such as small electric lights 93.

lVhen beginning drilling operations, the platform 2, carrying the drill operating mechanism, is moved to rearward position on the carrying or main frame, and the latter is moved forward toward the face of the rock to be drilled. As the drill spindles and drills will be normaly pressed forward ,operativeness of a drill.

by the fluid pressure on the hammers, the drills will strike against the surface of the rock as the main frame is moved forward. As soon as the drills bear against the face of the rock, the main frame is secured in place, if necesary, and the machine set in operation. At the beginning of the drilling operation, the hammers strike against the drill spindles lightly until the drills form holes of a sufficientdepth to serve as guides. As the drills penetrate. the platform is fed forward at a relatively faster rate and the blows of the hammers increase in force proportionally to the relatively forward movement of the platform, carrying the drilling mechanism. Until after the initial holes have been formed by the drills, the forward movement of the platform will be controlled by the operator as hereinafter described. It will happen. not infrequently, that one of the drills, or more. will strike a very hard spot,

or forsome other reason will be prevented fronipenetig'ating the rock, and hence as the platform is moved forward, the front face of the box 72. carrying the drill spindles, will approach the heads 9t on the spindles in which the drills are secured; If the movement of the platform is allowed to continue, the box will strike against the head carrying the inoperative drill, preventing any further movement of the platform, and if the feed of the platform is positive, will probably cause an injury to some portion of the machine. Inorder to prevent such a contingency, provision is madefor warning the operator and also for stopping the drilling operation and withdrawing the platform before injury can result from the in Such indications may be given by providing means whereby an electric circuit including a lamp orother indicators, is closed by some movable portion which will continue to advance when the drill fails to advance. In the construction shown in Figs. 11 and 14:, two contact fingers 95 and 96 are so attached to blocks of insulating material, secured to the front face of the box 72 as to be in the line of movement of the heads 9 L, on the drill spindles. the springs being so shaped that the heads will contact with them in succession. Both springs are included in a circuit of a generator, said circuit also including the machine. ln the circuit of the fingers 95, against which the spindle heads will first hear. are included indicators 88 as an electric light, see Figs. 1 and 14. In the circuit of the other fingers 96, is included a solenoid 99 which will become excited when any of the heads 94 strike against the fingers 96. See Figs. 1 and 14.

By movement of the core of the solenoid, an arm 100 is shifted, said arm being connected by ashaft- 101 to a lever 192, which is adapted to be detachably connected by a hook 103 to another lever 104; secured to the plug of a fourway valve 105, adapted to control the flow of liquid to and from the cylinders 106 and 107. The piston rod of the cylinder 106 is adapted when shifted in one direction, to strike against the lever and thereby shift the clutch mechanism 32 to open position, disconnecting the power.

shaft 21 from which the various mecha-, nisms, herembefore described, are operated. Sln'iultaneously with the shifting of the lever 31, a lever 29 is also shifted through.

the medium of a detachable connection the clutch 32 and of the rack 26 from the pinion should precede any movement of the main frame, the movement of the valve by its lever 104 is such as topermit the flow of liquid into the right hand end of the cylinder 106see Fig. 2-and to permit the escape of fluid from the opposite end of the cylinder, thus effecting the movement to the left of the piston in the cylinder 106, in

Fig. 2, and the consequent shifting of lever 31. The movement of this piston effects as before stated, the disengagement of the members of the clutch 32 and ofthe rack 25 from the pinion, so that by thetime said piston has moved beyond the port to which the pipe 111 is connected, the main frame is free to move. By theflow of fluid from cylinder 106 through this pipe 1,11 to the,

cylinder 107, such cylinder will be shifted to the left in Fig. 2, the cylinder being connected to the platform 2 and its piston to the main frame of the machine so that by the shifting of this cylinder, the platform will be drawn back or to the left in Figs.

1, 2, 3, and 4:, thereby withdrawing the several drills from the holes in which they were operating in the rock.

In the operation of the machine after the drills have been properly adjusted on their several spindles, the lever 1041- of the valve controlling the flow of fluid to the cylinders is shifted, thereby turning the valve to such position that fluid will flow into the right hand end of cylinder 107 and to the left hand end of cylinder 106. The entrance of the fluid into cylinder 106 withdraws the piston rod 108 and the flowof fluid into the right hand end of cylinder 107 will shift the platform forward so that the spindle box 7 2 will be brought adjacent to the face quired for the drills to form initial or guide holes in the rock, the operator will control the forward movement of the platform by The lever 31 is then shifted,

the lever 10-l connected to thevalve mechanism, controlling the flow of fluid pressure into the right hand end of tne cylinder 10?.

As soon as the guide holes have been formed, the valve is shifted to mamtam suf ticient pressure in cylinder 10? to more the platform forward, as the lever 29 is shifted to raise the rack bar 26 into engagement with the pinion 25. This mechanical'connection between the platform and the shaft 1 does not effect a forward movement of the platform, but operates as a governor controlling; the movement effected by fluid pressure in the cylinder 10?. It will be understood that although the mechanical connection is employed primarily as a fi'OVBT- nor, it will be used to assist in the forward v movement of the platform.

l/Vlien, in the operation of drilling, one of the drills should become stuck in the hole, its driving connection formed by the ball 89 will be released and at the time its contact finger 91 is shifted so as to close the circuit through an indicator, as a small electric light, and also through the solenoid 99. As hereinbefore stated, the u'iovement of the core of the solenoid will disconnec the mechanical parts employed in shifting the platform forward, and thereupon the of the rock, so that the drill. which has stuck can be removed from its hole and replaced 1 by another and smaller drill.

When in the operation of drilling, the spindle head 94 of one or more of the drills is forced back or rather prevented from advancing with the others, a contact is first made through indicating lights to warn the operator to lessen the forward feed of the platform, in order that the ineffective drill can work its way into an equal depth with the others. If the operator fails to notice the indication, the spindle head will force the contact spring against its other mei'nber, spring 96, closingthe circuit through the solenoid with the resulting withdrawal of the platform, as hereinbefore indicated.

In some cases it is desirable to prevent pieces of rock from falling out from the face of the rock, and in such cases, a shield or head or plate 122 is employed, as shown in Figs. 3, a and 17. This shield or head is secured to the outer ends of rods 123 which are movably mounted in bearings 1241: on the spindle head or box 7 2. This shield is pro-- vided with sleeves .125 through which the drills can move freely. The shield is provided with spring buffers 126 adapted to bear against the rock at points intermediate the holes formed by the drills. The support ing; rods extend back into the cylinder 48, so that the pressure therein will yieldingzly hold the head or shield in position while the drills move through it and into the rock. In

iii

case it is desired to use water or otli" in the drilling operation, the head or may be made hollow and connected pipe 128 with a suitable source of supply. The front face of the shield is pro-- vided with nozzles 12? suitably arra ed for directing the fluid on the rock or into the holes formed by the drills.

I claim herein as my invention 1. In a mining machine, the combir'zation a cylinder, a plurality of ham i hav ing portions extending into said 'ylinder and adapted to be forced outwardly by fluid pressure within the cylinder, and means for .=-;hifting said hammers against the press ire of the fluid.

2. In a mining machine, the combination of a cylinder, a plurality of hamn'iers having portions extending into said cylinder and adapted to be forced outwardly by fluid pressure within the cylinder and means adapted to engage the hammers at any point within their range of movement and draw :1 vin inwardly against the pressure in the .eylinder.

In a mining machine, the combination of a platform, a plurality of means for mo ing the platform towards and from the face of rock to be drilled, a plurality of drill operating means carried by the platform, means for controlling the movement of the platform and in turn controlled by each of v the drill operating means.

l. In a mining machine, the combination of a platform, means for n'ioving the platform towards and from the face of rorl: to be drilled, a plurality of drill operatine means carried by the platform and means operative in case a drill fails to advance at substantially the same rate as the other drills to effect a reversal of the movement of-the platform.

5. In a mining machine the combination of a main frame, a platform movable in said frame, a plurality of hammers carried by the platform, a plurality of drill spindles and means for operating the hammers whereby the stroke of the hammers may vary inversely proportionally to the penetration of the drills into the rock.

6. In a mining machine, the combination of a cylinder, a plurality of hammers extending into said cylinder and subjected to pressure tending to move the hammers outwardly, a pulling head arranged within the cylinder provided with a plurality of means for engaging the hammers regardless of the relative positions of the hammers.

7. In a mining machine, the combination of a plurality of drills, a plurality of hammers for forcing said drills forward, and means for indicating to the operator the ,amsao failure of drill to advance at su the same rate as the other drills.

8. In a mining machine the combination of a plurality of hammers, a plurali y of drill spindles and means for operating the hammers whereby the stroke of the hammers may vary inversely proportionally to the penetration of the drills into the rock.

9; In a mining machine, the combination of a plurality of drills, means for driving said drills forward, a plate having openings therethrough for the longitudinal moven" of the drills and means for yieldingly 1 i ing. of the plate against the face of the material being operated on.

10. In a mining machine, the. combination of a platform, a drill operating mechanism carried by the platfo in, means for moving the platform forward, a plate provided with openings adapted'to permit of the movement of the drills therethrough and fluid pressure means for yieldingly holding:- the plate against the face-of the material operated on by the drills.

11. In mining machine, the combination of a plurality of drills, means for driving said drills forward, a hollow plate having openings therethrough adapted to permit of the longitudinal movement of the dri ls therethrough, and provided with outlets adjacent to the openings, means for forciiug; fluid into the plate, and means for yieldingly supporting the plate adjacent to the face of the material operated on by the drills.

12. In a miningmachine the combination of a plurality of drills, a plurality of mechanisms for rotating said drills and indi t lting mechanism for indicating to the op rator the failure of a drill to rotate.

18. In a mining machine the combinal ion of a platform, means for moving the plat form towards and from the face of the material to be operated on, a plurality of drill rotating means carried by the platform and means operative in case a drill fails to ro tate in unison with its operating means to effect a reversal of the movement of the platform.

14. In a mining machine, the comoination of a rotating head, a sleeve passing through said head, means for locking the sleeve to the head, such means being adapted to move to unlocking position in case the sleeve encounters abnormal resistance to its rotation, and a drill spindle adapted to move longitudinally through the sleeve and to rotate therewith.

my hand.

GEORGE R. BENNETT. 

